Previously across the National Transmission System (NTS), we used a three-part epoxy grout for pipe repairs such as corrosion damage, cracked welds and laminations.
While extremely durable, these grouts which consisted of a resin, filler powder and hardener, had their limitations. In June 2017, we launched an Epoxy Grout Investigation project, to explore the possibility of using a higher specification of epoxy grout on our network.
Preparing the grout involved mixing the three individual components, a task which was difficult for the operations technicians when carried out on site during wet or windy weather conditions. Secondly, depending on the time of the year, the grout often hardened either too quickly or too slowly, which was a potential risk to the repairs being carried out.
In June 2017, we launched an Epoxy Grout Investigation project, working with Namco Solutions Ltd, to explore the possibility of using a higher specification of epoxy grout on our network.
As part of the project, Namco were asked to develop a two-part epoxy grout, where the filler powder and resin were combined, to make mixing easier. Namco developed two grades of grout for use at different times of the year – winter and summer. The new grades were different colours – blue for winter and red for summer – so that the curing process was applicable to the time of the year.
Following the development of these new grades, we assessed and proved their effectiveness through a series of lab-based tests, conducted at DNV’s facility in Loughborough.
These tests were used to explore their short-term strength and adhesiveness, as well as their long-term performance, by exposing them to extreme temperatures. They identified that:
- The winter grade epoxy grout has an installation temperature range of between +5°C and +20°C, and an operating temperature range between -40°C and +70°C
- The summer grade epoxy grout has an installation temperature range between +20°C and +35°C, and an operating temperature range between -40°C and 100°C
They also proved that the winter grout can keeps its strength up to 70°C and the summer grout maintains its strength up to 100°C.
Because these epoxy grades stay strong at higher temperatures, we can use them on high-pressure pipelines where the working temperature is more than 60°C. Previously, work on these pipelines would require more complex and expensive repairs.
Following completion of the project, the new epoxy grouts are available for technicians to use on our network, particularly for those jobs where the pipes run at higher temperatures.